1. Field of the Invention
The present invention relates to a semiconductor storage medium removably installable in an electronic device.
2. Description of the Related Art
Recently, various data recording and/or playback apparatuses such as a digital still camera have been prevailing. There has been developed a variety of external memories removably installable in such electronic devices and are also portable. Typical ones of the external memories are semiconductor memories such as a flash memory.
Such an external memory can record together data whose formats are different from each other, such as still image data, moving image data, audio data (music data), etc. Therefore, the user can use such an external memory in common with a plurality of electronic devices which deal with data whose formats are different from each other.
Namely, the user can use the external memory with a digital still camera for example to play back and view still image data stored in the external memory. Alternatively, the user can use the external memory with a digital video camera for example to play back and view moving image data recorded in the external memory.
As one example of the external memories, there is available a conventional semiconductor memory having an appearance as shown in FIGS. 1A and 2B. The semiconductor memory is generally indicated with a reference 200. The semiconductor memory 200 is encased in a housing 201 having a length of 50 mm, width of 21.5 mm and a thickness of 2.8 mm for example. The semiconductor memory 200 further has a 10-pin terminal 202 through which a state of a serial bus, various data, clock, etc. are sent when the semiconductor memory 200 is installed in an external electronic device. In addition, the semiconductor memory 200 has a safety switch 203 provided to prevent data recorded in the semiconductor memory 200 from inadvertently being erased.
As shown in FIG. 2, the semiconductor memory 200 further includes a flash memory 204 of several megabytes to tens megabytes for example to store various data from the electronic device in which it is installed, a memory controller 205 to manage the content of the flash memory 204, and an interface 206 provided for connection to the electronic device and to and from which various data are supplied and delivered.
In the semiconductor memory 200, only three pins, data, clock and bus state, respectively, of the 10-pin terminal 202 are used to send the data, clock and bus state between the semiconductor memory 200 and electronic device. Note that the clock and bus state are supplied from the electronic device to the semiconductor memory 200 while the data is sent between the semiconductor memory 200 and electronic device by the bidirectional half-duplex transfer. To send a control packet as the data between the semiconductor memory 200 and electronic device, the maximum frequency of the clock is 20 MHz for example and an error check code in units of 512 bytes is added to the control packet.
The semiconductor memory 200 operates according to a protocol of the serial interface under the control of the memory controller 205 to control the flash memory 204.
More specifically, if the semiconductor memory 200 uses the flash memory 204 including a plurality of flash memories for example, each of the flash memories is controlled by the memory controller 205. Also, if the semiconductor memory 200 uses the flash memory 204 including, for example, a plurality of flash memories whose types are different from each other, the memory controller 205 controls each of the flash memories according to the characteristic of each flash memory, and corrects error correspondingly to the error characteristic of each flash. Further, the semiconductor memory 200 converts parallel data to serial data by the memory controller 205.
Since the semiconductor memory 200 operates according to the protocol of the serial interface under the control of the memory controller 205, it can employ any of the currently available flash memories.
The semiconductor memory 200 uses a hierarchical file system based on FAT (file allocation table) normally installed in personal computers. Based on the FAT-based hierarchical file system, the semiconductor memory 200 stores into the flash memory 204 a plurality of data whose formats are different from each other, such as still image data, moving image data, audio data (music data) and voice data (speech data), and controls the content of the flash memory 204 by the memory controller 205. In the semiconductor memory 200, a file format and directory management method used for recording data in the flash memory 204 are previously defined for each data format. The semiconductor memory 200 manages data recorded into the flash memory according to the defined format and directory management method.
More specifically, as shown in FIG. 3, there are recorded in the root directory in the flash memory 200 “MEM*****.ind” which is a file indicating the type of the semiconductor memory 204, “DCMI” which is a directory in which f still picture file is stored, “VOICE” which is a directory in which a voice file is stored, “HIFI” which is a directory in which an audio file is stored, “CONTROL” which is a directory in which appended information such as control information file is stored, and “MS*****” which is a directory in which information peculiar to the vendor is stored.
The semiconductor memory 200 adopts as the still image data format called DCF (design rule for camera file system) standardized by the JEIDA (Japanese Electronic Industry Development Association), and as the format of audio data ADPCM (adaptive difference pulse code modulation) of the Recommendation G.726 of the ITU-T (International Telecommunication Union).
The user can use the semiconductor memory 200 as an external memory in common with a plurality of electronic devices which deal with data whose formats are different from each other.
The semiconductor memory 200 can be used as in the following for example. With the semiconductor memory 200 installed in a digital still camera, image data is stored into the semiconductor memory 200. The semiconductor memory 200 is removed from the digital still camera, and installed into a personal computer for example. The image data thus stored in the semiconductor memory 200 can be transferred to a recording medium in the personal computer, printed out by a printer connected to the personal computer or displayed on a monitor provided on or connected to the personal computer.
However, if the semiconductor memory is not installed in the digital still camera when it is desired to pick up an object easily and instantly, it is not possible to timely trip the camera shutter.
Of a system in which while an object is being picked up, a captured picture is displayed on the monitor of a personal computer, the camera such as the digital still camera is too large to easily carry on.